Intrinsically conductive polymers (ICPs) are known for a wide range of applications including use in printed organic circuits and in organic electronic devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices.
An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.
Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light-emitting material combine to form an exciton that releases its energy as light.
Suitable light-emitting materials include small molecule, polymeric and dendrimeric materials. Suitable light-emitting polymers include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as polyfluorenes.
A hole-transporting or hole-injecting layer may be provided between the anode and light-emitting layer of an OLED. WO 2012/131314 discloses a hole-transporting layer of a polymer doped with partially fluorinated fullerene.
WO 2012/086668 discloses polymers comprising repeat units of formula (1):
wherein n1 and n2 are each an integer of 1 to 5. WO 2012/086668 describes formation of these polymers by Suzuki polymerisation, wherein carbon-carbon bonds are formed between aromatic groups of monomers.
US2007/205714 discloses polymers comprising at least 5 mol % of repeat units of the following formula:
wherein X is —CR1═CR1—, C≡C or N—Ar and Y is a divalent aromatic or heteroaromatic ring system having 2 to 40 C atoms.
One method of forming ICPs is the Buchwald-Hartwig polymerisation process in which an aryl dihalide monomer is reacted with a monomer containing primary or secondary arylamines in the presence of a palladium catalyst. In the Buchwald-Hartwig polymerisation process a C—N bond is formed between an aromatic carbon atom of an aromatic monomer and a N atom of an arylamine monomer.
US 2004/262574 discloses a method of forming polymers according to the following general process:

In which Ar1, Ar2, Ar3 and Ar4 are aromatic groups, X1 and X2 are halogens, polymer termini B and C represent a hydrogen or halogen atom, m is an integer of at least 1 and n is an integer of at least 2.
Another method of forming ICPs is Suzuki polymerisation, for example as described in WO 00/53656, WO 03/035796 and U.S. Pat. No. 5,777,070. During Suzuki polymerisation, which takes place in the presence of a palladium catalyst, carbon-carbon bonds form between aromatic carbon atoms of monomers.